中文摘要：

在相对感纹枯病品种Lemont的第11染色体上存在1个抗性QTLqSB-11（抗性等位基因为qSB-11b）。对qSB-11“的育种效应即挽回产量损失率进行了研究。在纹枯病较轻发生（4级左右）情况下，qSB-11Le基本未表现出明显的育种效应，相反在重发生（8级左右）条件下，qSB-11Le能挽回的产量损失率达到10．71％。利用发展的多态性分子标记及Bc4F2代分离群体，qSB-11Le的存在区间被缩小到分子标记Z405与Z286之间，物理距离在1000kb左右。可以认为，在水稻抗纹枯病分子育种中，qSB-11Le具有较大的育种价值，利用研究发展的多态性标记可以提高qSB-11Le的选择效率。

英文摘要：

The breeding effect of a resistant QTL qSB-11, with a resistant allele （qSB-11^Le） for the rice sheath blight located on chromosome 11 of a susceptible variety Lemont, was investigated. Under severe disease conditions, the lines carrying the qSB-11^Le allele could reduce yield loss up to 10.71% compared to those without this allele. However, no significant difference in yield between the two lines was noted when they were disease-free or slightly infected. By using polymorphic markers and BC4 Fz segregating population at the region containing qSB-11 L,, the interval covering qSB-11Le was reduced to 1000 kb in length between the two molecular markers, Z405 and Z286. Therefore, the qSB-11^Le allele was considered to have a considerable potential in breeding for resistance to rice sheath blight. The molecular markers linked to qSB-11 Le developed in the study would be useful to incorporate this favorite allele into elite rice lines via marker assisted selection （MAS）.